U.S. patent application number 14/798752 was filed with the patent office on 2016-01-28 for agricultural vehicle.
The applicant listed for this patent is CLAAS INDUSTRIETECHNIK GMBH. Invention is credited to Carolin Hammacher, David C. Janzen, Robert Obermeier-Hartmann, Ronald L. Satzler, Thomas Schulte, Hendrik Schultze Zumkley.
Application Number | 20160023695 14/798752 |
Document ID | / |
Family ID | 53365797 |
Filed Date | 2016-01-28 |
United States Patent
Application |
20160023695 |
Kind Code |
A1 |
Obermeier-Hartmann; Robert ;
et al. |
January 28, 2016 |
Agricultural vehicle
Abstract
An agricultural vehicle having a full-track design with a
vehicle structure on each side of which, relative to a vehicle
longitudinal axis, a track roller unit is arranged. The track
roller unit has roller unit body to which a front deflector roll, a
rear deflector roller and a plurality of yoke-type track rollers
arranged therebetween are coupled, and an endlessly closed track
belt that wraps around the rollers/roller. All the rollers are
suspended with respect to the roller unit body in that assigned to
a roller or a group of rollers in each case is a spring element,
which is acted upon by fluid, for the suspension thereof with
respect to the roller unit body.
Inventors: |
Obermeier-Hartmann; Robert;
(Bueren, DE) ; Zumkley; Hendrik Schultze;
(Rietberg, DE) ; Schulte; Thomas; (Delbrueck,
DE) ; Satzler; Ronald L.; (Princeville, IL) ;
Janzen; David C.; (Metamora, IL) ; Hammacher;
Carolin; (Freiberg, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
CLAAS INDUSTRIETECHNIK GMBH |
Paderborn |
|
DE |
|
|
Family ID: |
53365797 |
Appl. No.: |
14/798752 |
Filed: |
July 14, 2015 |
Current U.S.
Class: |
180/9.54 |
Current CPC
Class: |
B62D 55/305 20130101;
B60G 2300/08 20130101; B62D 55/06 20130101; B62D 55/112 20130101;
B62D 55/1125 20130101; B60G 2300/32 20130101; B62D 55/30
20130101 |
International
Class: |
B62D 55/112 20060101
B62D055/112; B62D 55/30 20060101 B62D055/30; B62D 55/06 20060101
B62D055/06 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 25, 2014 |
DE |
102014110551.6 |
Claims
1. An agricultural vehicle having a full-track design and a vehicle
structure, on each side of which, relative to a vehicle
longitudinal axis, a track roller unit is arranged in order to
support the vehicle with respect to the ground, the track roller
unit comprising: a roller unit body, to which a front deflector
roll, a rear deflector roller and a plurality of yoke-type track
rollers arranged therebetween are coupled; and an endlessly closed
track belt, which wraps at least around the front deflector roller
and the rear deflector roll, along which the yoke-type track
rollers; wherein all the rollers of the track roller unit are
suspended with respect to the roller unit body in that assigned to
a roller or a group of rollers in each case are spring elements
that are acted upon by fluid for suspension thereof with respect to
the roller unit body.
2. The agricultural vehicle according to claim 1, wherein the
roller unit body is attached to the vehicle structure.
3. The agricultural vehicle according to claim 1, wherein the
roller unit body of the track roller unit is an integral component
of the vehicle structure.
4. The agricultural vehicle according to claim 1, wherein the track
roller unit further comprises means for distributing a ground
pressure proceeding from the vehicle onto individual spring
elements, onto one or more groups of the spring elements or
both.
5. The agricultural vehicle according to claim 1, wherein the track
roller unit further comprises a fluid system for supplying the
spring elements and wherein certain of the spring elements are
selected depending on an event are interconnected in a separate
fluid circuit in order to form a suspension unit.
6. The agricultural vehicle according to claim 5, wherein the
suspension unit formed by the separate fluid circuit has a pendulum
point (P.sub.a, P.sub.b), which forms a virtual axle of the
agricultural vehicle.
7. The agricultural vehicle according to claim 5, wherein at least
one of the spring elements of the track roller unit is assigned to
a front suspension unit in order to form a virtual front axle and
at least one of the spring elements of the same track roller unit
is assigned to a rear suspension unit in order to form a virtual
rear axle.
8. The agricultural vehicle according to claim 7, wherein at least
one yoke-type track roller is assigned either to the virtual front
axle or to the virtual rear axle, depending on an operating
parameter of the vehicle comprising a pressure load, a vehicle
state or both, by connecting the associated spring element to a
corresponding fluid circuit.
9. The agricultural vehicle according to claim 8, wherein the
spring elements are assigned sensors for detecting a pressure state
therein and wherein at least one of the yoke-type track rollers is
assigned depending on the detected pressure state one or more of
the spring elements.
10. The agricultural vehicle according to claim 1, further
comprising means for influencing a pressure distribution between
spring elements positioned in a front portion of the track roller
unit and spring elements positioned in a rear portion of the track
roller unit depending on a detected tractive force (F.sub.Zug) of
the vehicle.
11. The agricultural vehicle according to claim 7, further
comprising means for influencing the fluid pressures of a fluid
circuit associated with the virtual front axle, a fluid circuit
associated with the virtual rear axle or both depending on detected
operating parameters of the vehicle.
12. The agricultural vehicle according to claim 11, wherein the
vehicle is operated in a street-travel mode, in which the spring
elements of the virtual front axle are acted upon by a pressure
that is reduced as compared to that of a field-travel mode.
13. The agricultural vehicle according to claim 7, wherein the
spring elements of the virtual front axle are acted upon by a
pressure that depends on an applied tractive force (F.sub.Zug) of
the vehicle in order to reduce a sum of effective torques at the
track roller unit.
14. The agricultural vehicle according to claim 10, wherein spring
element in the rear portion of the track roller unit is acted upon
by increased fluid pressure via individual control in order to
prevent the track roller unit from lifting up in an event of
particularly high tractive force (F.sub.Zug).
15. The agricultural vehicle according to claim 1, wherein one or
more rollers are coupled to the roller unit body via linkages.
16. The agricultural vehicle according to claim 1, wherein the
front deflector roller and a yoke-type track roller located behind
the front deflector roller relative to the vehicle longitudinal
axis are connected to the roller unit body via a common support
arrangement and wherein one of the spring elements is assigned to
the support arrangement for suspension thereof with respect to the
roller unit body.
17. The agricultural vehicle according to claim 16, wherein the
common support arrangement comprises a longitudinal swing arm
coupled to the roller unit body, wherein an arm is coupled to the
longitudinal swing arm, wherein the front deflector roller is
supported at the arm, wherein one of the yoke-type track rollers is
supported at the longitudinal swing arm and wherein a tensioning
device is assigned to the arm that is acted upon by fluid pressure
in order to apply tension in the track belt.
18. The agricultural vehicle according to claim 17, wherein the
tensioning device is a cylinder.
Description
CROSS-REFERENCE TO A RELATED APPLICATION
[0001] The invention described and claimed hereinbelow is also
described in German Patent Application DE 10 2014 110551.6, filed
on Jul. 25, 2014. The German Patent Application, the subject
matters of which is incorporated herein by reference, provides the
basis for a claim of priority of invention under 35 U.S.C.
119(a)-(d).
BACKGROUND OF THE INVENTION
[0002] The present invention relates to an agricultural vehicle, in
particular, a tractor or a harvesting machine having a full-track
design and a vehicle structure on each side of which a track roller
unit is arranged that comprises a roller unit body to which a front
deflector roll, a rear deflector roller and a plurality of
yoke-type track rollers arranged therebetween are coupled and an
endlessly closed track belt that wraps at least around the front
deflector roller and the rear deflector roller along which the
yoke-type track rollers roll.
[0003] It is known to equip agricultural vehicles such as tractors
or harvesting machines with track roller units, which have a larger
ground contact area than wheels and therefore have a greater
transfer of tractive force with less slip and result in less ground
compression. The designs of track-type tractors available on the
market can be subdivided into pivot-steered four-track tractors,
two-track tractors and half-track tractors.
[0004] Pivot-steered four-track tractors are usually found in the
upper performance class and, due to their weight and size alone,
are less suitable for transport tasks or lighter applications.
[0005] Two-track tractors have a track roller unit on each side of
the vehicle, relative to the longitudinal axis of the vehicle,
which is used to support the vehicle with respect to the ground
(full-track design). The track roller units can usually rotate by a
small angle about a vehicle transverse axis relative to the vehicle
frame, wherein the vehicle frame is designed largely identical to
that of a corresponding wheel tractor. Reference is made in this
context to WO1998/40266, merely as an example. Two-track tractors
must be designed to be nose-heavy, in order to obtain a uniform
pressure distribution under the track roller units when the work
operation utilizes tractive force.
[0006] A uniform distribution of pressure is desired in the case of
pulling work, in particular, because this is the only way to
utilize the full potential in terms of the transfer of tractive
force and protecting the ground. The nose-heaviness required
therefor is a disadvantage of conventional two-track tractors,
however. The reason is that, in order to achieve the aforementioned
advantages, there must be good coordination with the particular
drag of the attached implement. However, since the drag can vary
greatly between various implements and/or depending on the
particular working conditions (e.g., soil properties, tilling
depth, ground speed, etc.) in practical applications, an operator
must compensate therefor by attaching a suitable front ballast on
the vehicle before starting to drive. If tractive forces fluctuate
during operation, it is no longer possible to apply ballast
correctly. When the nose-heavy vehicle travels on asphalted roads,
the tread bars of the track belt, which are usually made of rubber,
are strongly braked and compressed upon entry into the latch, which
results in high wear and associated increased operating costs of
the vehicle.
[0007] Half-track tractors are usually converted wheel machines, in
which, e.g., the rear wheels are replaced with track roller units.
The altered transmission ratio results in a great reduction of the
maximum speed. Track roller units also must be mounted on the front
in the case of four-wheel drive tractors, due to the fixed
transmission ratio between the front axle and the rear axle. In
this context, reference is made to US 2007/0261898 A1 as an
example. In addition to an altered suspension behavior of the
overall vehicle, reduced operational reliability must be
accepted.
[0008] WO 2013/113484 A2 makes known another concept for a
half-track vehicle. In this case, the (rear) track roller unit is
used as a drive element. The front axle (which is designed as a
wheel axle) is used only to support vertical forces and as steering
support. In this dual-axle vehicle, the track roller unit is
suspended in the manner of a pendulum. The track therefore lifts up
when tractive force is generated. This is avoided by controlled
counterpressure of a hydraulic cylinder. The front axle is relieved
by applying tractive force and by the force of the hydraulic
cylinder. It is therefore possible to hold the pressure
distribution under the track roller unit constant during field
work. During road travel, however, the hydraulic force can be
reversed and, therefore, the front deflector roller of the track
roller unit can be relieved. The front axle (wheel axle) therefore
assumes a greater load. This results in a more gentle entry by the
track bars and therefore reduces wear. As compared to the classic
two-track tractor, this concept provides advantages both on
yielding ground and on hard ground. The front axle additionally
reduces pitching oscillations and, therefore, increases driving
comfort.
[0009] Since the vehicle described in VVO 2013/113484 A2 has a
non-driven front axle, the disadvantage of having to provide
precise ballast exists in this case as well. A front axle load of
zero would be ideal for tractive efficiency. In this case, there is
a risk, however, that the vehicle could tip backward and therefore
the front axle must remain loaded to a slight extent. This load
cannot be used to transfer tractive force, however, and can
compress the ground if the tires are too small. It would be
conceivable also to drive the front axle. It would be too complex
to adjust the advance that is required due to the different
tractive force characteristics of wheel and track, however,
especially since agricultural tractors are usually not equipped
with an interaxle differential.
[0010] In addition to a hydraulic element on the track roller unit,
the vehicle according to WO 2013/113484 A2 also has a high-value
steering axle. Due to the low intended front axle load, the vehicle
is equipped with differential steering in the rear axle, with which
the Ackermann steering system of the front axle must be
synchronized. In light of the above-described aspects, the overall
complexity of the vehicle is high.
SUMMARY OF THE INVENTION
[0011] The present invention overcomes the shortcomings of known
arts, such as those mentioned above.
[0012] To that end, the present invention provides a vehicle of the
initially mentioned type, by which, given a reasonable design
complexity, uniform support is obtained over a majority of the
roller unit length also in the event of different ballasts and
tractive forces, wherein the objective is reduce the wear of the
track belt during road travel and, in general, to increase the
driving comfort.
[0013] In an embodiment, the invention provides a tractor or a
harvesting machine having a full-track design and a vehicle
structure on each side of which a track roller unit is arranged
that comprises a roller unit body to which a front deflector roll,
a rear deflector roller and a plurality of yoke-type track rollers
arranged therebetween are coupled and an endlessly closed track
belt that wraps at least around the front deflector roller and the
rear deflector roller along which the yoke-type track rollers roll.
All the rollers of the track roller unit are suspended with respect
to the roller unit body in that assigned to a roller or a group of
rollers in each case is a spring element, which can be acted upon
by fluid, for the suspension thereof with respect to the roller
unit body.
[0014] By the inventive suspension of all rollers with respect to
the roller unit body, the vehicle weight is uniformly accommodated
in a wide range, i.e., along the entire effective length of the
track roller unit, in the event of different ballasts and tractive
forces and is supported on the ground. As compared to classic
two-track tractors, the risk of soil compression caused by
imprecise ballast application is therefore substantially reduced
and the capability of transferring tractive force is increased.
Given that, according to the invention, a roller or a group of
rollers has assigned thereto a spring element that is acted upon by
fluid for the suspension thereof with respect to the roller unit
body, the suspension behavior of the vehicle is influenced in a
controlled manner. The reason is that spring elements that are
acted upon by fluid have the advantage of compensating in a less
abrupt manner as compared to steel or rubber springs, the
characteristic curves of which must always suffice for the greatest
possible load. In addition, these are easily adapted to the load
and vary their damper to a great extent. So-called Hydrops are
preferably used for this purpose, i.e., hydropneumatic spring
elements, preferably with a level control system. The use of spring
elements that are acted upon by fluid advantageously makes it
possible to influence the acting contact forces, in order to
thereby relieve or load a part of the track roller in a controlled
manner as needed. As a result, reduced track bar wear occurs during
road travel, for example, or a more uniform pressure distribution
under the track roller unit occurs during pulling work, which, in
turn, protects the ground and increases the tractive force
efficiency. Such a suspension of the rollers also makes it possible
to increase the driving comfort in general, since the load is
adjusted and the spring characteristics can, in fact, be changed.
In addition, the relatively great roller unit length (full-track
design) results in low susceptibility of the vehicle to pitching
oscillations.
[0015] Various structural configurations of the vehicle are
conceivable. According to an embodiment, the roller unit body of a
track roller unit is attached to the vehicle structure. In this
case, the roller unit body is a separate component, to which the
associated deflector rollers and yoke-type track rollers of the
track roller unit are coupled and which is attached to the side of
a vehicle structure, e.g., via a flange connection.
[0016] In an embodiment, the roller unit body of a track roller
unit is an integral component of the vehicle structure. In this
case, the roller unit body is not designed as a separate component,
but rather is part of the vehicle structure. The deflector rollers
and yoke-type track rollers are therefore coupled to the vehicle
structure, e.g., by shafts and/or axles which are supported with
respect to the vehicle structure and protrude laterally
therefrom.
[0017] Very generally, in particular independently of the design of
the vehicle structure and the roller unit body, the vehicle
provides means for distributing a ground pressure proceeding from
the vehicle onto individual spring elements and/or onto one or more
groups of spring elements. Basically this can be any means with
which a ground pressure can be distributed, the ground pressure
being caused, in particular, by the weight of the vehicle.
[0018] Advantageously, the vehicle has a fluid system for supplying
the spring elements that are acted upon by fluid, in which certain
spring elements, which can be selected, in particular depending on
the event, are interconnected in a separate fluid circuit (or are
permanently interconnected) in order to form a suspension unit. By
interconnecting a plurality of spring elements in a fluid circuit,
which is closed per se, an identical fluid pressure is present at
all of the spring elements associated with the thusly formed
suspension unit such that, advantageously, a uniform load
distribution on the applicable spring elements or rollers
associated therewith automatically (autonomously) sets in.
[0019] Various embodiments of the arrangement are conceivable.
Advantageously, a suspension unit formed by a common fluid circuit
has a pendulum point, which forms a virtual axle of the vehicle. In
this case, the hydropneumatic suspension simulates an axle that can
pivot about this pendulum point.
[0020] In order to influence the load distribution of the vehicle,
it is furthermore advantageous to assign at least one spring
element of a track roller unit to a front suspension unit in order
to form a virtual front axle, and at least one spring element of
the same track roller unit can be assigned to a rear suspension
unit in order to form a virtual rear axle.
[0021] The above-described suspension concept can have diverse
designs. According to an advantageous development, at least one
yoke-type track roller of a track roller unit can be assigned to
either the virtual front axle or of the virtual rear axle,
depending on an operating parameter of the vehicle, by connecting
the associated spring element to a corresponding fluid circuit. By
the changeable assignment of the (at least one) yoke-type track
roller to either the front or the rear axle, it is possible to
reduce a pressure difference that may be present between the axles
by pressure compensation. The operating parameters to utilize can
be, for example: fluid pressure in the spring elements of the front
or the rear axle and/or yoke-type track roller, ground speed of the
vehicle. Advantageously, a hysteresis is provided in order to
prevent constant switching if the fluctuations about a limit value
are only slight. In addition, sensors for pressure detection are
expediently assigned to individual spring elements, wherein the
assignment to yoke-type track rollers is carried out depending on
the thusly detected pressure state of one or more spring
elements.
[0022] Advantageously, the vehicle is very generally equipped with
means for influencing a pressure distribution between front spring
elements and rear spring elements of the track roller unit
depending on the detected operating parameters of the vehicle, such
as the tractive force. It is therefore possible to adjust the
ground pressure underneath the track roller unit depending on the
operating state of the vehicle in order to increase the traction or
the tractive force efficiency, or to protect the ground.
[0023] Advantageously, this can be technically implemented by
providing the vehicle with means for influencing the fluid
pressures of separate fluid circuits between one another, in
particular a fluid circuit associated with the virtual front axle
and a fluid circuit associated with the virtual rear axle, and/or
for influencing the fluid pressure within a fluid circuit,
preferably depending on the detected operating parameters of the
vehicle in each case. The operating parameters that can be used
here are, e.g., tractive force of the vehicle, fluid pressure in
the spring elements of the front or the rear axle and/or yoke-type
track roller, ground speed of the vehicle.
[0024] In order to reduce the wear of the track belt, the vehicle
is advantageously operated in a road-travel mode, in which spring
element of the virtual front axle are acted upon by reduced
pressure as compared to a field-travel mode.
[0025] The efficiency and traction of the vehicle during use for
work, in particular for pulling work, is advantageously increased
in that spring elements of the virtual front axle are acted upon by
a pressure that is dependent on an applied tractive force of the
vehicle, in particular, with the goal of reducing the sum of
effective torques at the track roller unit, preferably bringing
this to zero.
[0026] Given that a rear spring element of the track roller unit is
acted upon by increased fluid pressure by individual control, the
track roller unit is prevented from lifting up in the event of
particularly high tractive force. The background of this function
is that a rear pendulum point of the track roller is displaced
further toward the rear by applying pressure to the rear spring
element, whereby the track roller unit remains in the lying
position even in the event of a high effective tractive force.
[0027] According to a structurally advantageous embodiment, at
least one or more rollers of a track roller unit are coupled to the
roller unit body. A linkage in this case can consist of one or more
retaining elements, which are connected to one another and can be
used to couple one or more rollers.
[0028] In an embodiment, the front deflector roller and a yoke-type
track roller, which is located behind this relative to the
longitudinal axis of the vehicle, are connected to the roller unit
body via a common support arrangement. Assigned to the support
arrangement is a spring element for the suspension thereof with
respect to the roller unit body. Advantageously, a virtual front
axle is formed by this support arrangement. Preferably, this is
designed such that the support arrangement comprises a longitudinal
swing arm, which is coupled to the roller unit body, and an arm,
which is coupled to the longitudinal swing arm. The front deflector
roller is supported at the arm and the yoke type track roller is
supported at the longitudinal swing arm. Assigned to the arm is a
tensioning device, preferably in the form of a cylinder, which is
acted upon by fluid pressure, in order to apply tension in the
track belt. It should be noted that various embodiments for a
virtual front axle are conceivable, including embodiments deviating
therefrom.
BRIEF DESCRIPTION OF THE DRAWINGS
[0029] Further features and advantages of the invention will become
apparent from the description of embodiments that follows, with
reference to the attached figures, wherein:
[0030] FIG. 1 depicts a schematic view from the side of an
agricultural tractor comprising a track roller unit;
[0031] FIG. 1a depicts a front part of a track roller unit, which
has an altered coupling of the front rollers as compared to the
track roller unit of the tractor shown in FIG. 1;
[0032] FIG. 1b depicts a front part of a track roller unit, which
has another altered coupling of the front rollers as compared to
the track roller unit of the tractor shown in FIG. 1;
[0033] FIG. 2a depicts the track roller unit of the tractor shown
in FIG. 1, with an indicated inner allocation of the roller
unit;
[0034] FIG. 2b depicts the track roller unit of the tractor shown
in FIG. 1, with a normal tractive load;
[0035] FIG. 2c depicts the track roller unit of the tractor shown
in FIG. 1, with an overload;
[0036] FIG. 3a depicts a track roller unit of a tractor having a
changeable inner allocation during road travel; and
[0037] FIG. 3b depicts a track roller unit of a tractor having a
changeable inner allocation during field travel.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0038] The following is a detailed description of example
embodiments of the invention depicted in the accompanying drawings.
The example embodiments are presented in such detail as to clearly
communicate the invention and are designed to make such embodiments
obvious to a person of ordinary skill in the art. However, the
amount of detail offered is not intended to limit the anticipated
variations of embodiments; on the contrary, the intention is to
cover all modifications, equivalents, and alternatives falling
within the spirit and scope of the present invention, as defined by
the appended claims.
[0039] FIG. 1 depicts a schematic view from the side of an
agricultural tractor 1 according to the invention during travel on
the field 5. The tractor 1 is designed with a full-track
configuration and has a vehicle structure in the form of a vehicle
frame 2. A track roller unit 4 is attached to the vehicle frame 2,
on both sides relative to a vehicle longitudinal axis 3 (indicated
by an arrow), i.e.; on the left and the right sides of the vehicle
frame 2. The tractor is supported with respect to the ground
exclusively via the two track roller units 4. Since the view is
from the side, only the track roller unit 4 on the left, relative
to the vehicle longitudinal axis 3, is visible in FIG. 1. A right
track roller unit, which has a design identical to that of the left
track roller unit 4 shown, is located correspondingly on the right
side of the frame 2. Since the two track roller units have an
identical design, the descriptions of the left track roller unit 4
provided in the following apply equally to the right track roller
unit.
[0040] In order to carry out intended work, such as pulling work,
the tractor 1 is equipped with at least one suitable coupling
device in a manner that is known per se and is therefore not shown
in greater detail, thereby allowing an implement (e.g., a tillage
implement, such as a plow) to be pulled by the tractor 1. It should
be noted that the invention is described here using a tractor 1 as
an example, but is not limited to this type of agricultural
vehicle. As an alterntive, the vehicle could be, e.g., a
self-propelled harvesting machine such as a combine harvester,
forage harvester, or a baler.
[0041] As indicated in FIG. 1, the track roller unit 4 of the
tractor 1 comprises a roller unit body 6. This is rigidly connected
to the vehicle frame 2, e.g., via a flange connection. The
following are coupled to the roller unit body 6 by means of
linkage, which will be explained further below: a front deflector
roller 10, a rear deflector roller 20, and a plurality of (e.g,
five) yoke-type track rollers 11, 12, 13, 14, 15 arranged
therebetween. It should be noted that, instead of the embodiment
shown (comprising a roller unit body 6 attached to the vehicle
frame 2), it is conceivable that the roller unit body of a track
roller unit is an integral component of the vehicle structure. In
this (non-illustrated) case, the deflector rollers and yoke-type
track rollers would be coupled to the vehicle structure, which also
functions as a roller unit body in this case.
[0042] In the embodiment of FIG. 1, in the front region of the
track roller unit 4, an endlessly closed track belt 7 wraps around
half (i.e., with a wraparound of 180.degree.) of the front
deflector roller 10 and, in the rear region of the track roller
unit 4, wraps around half of the rear deflector roller 20. The
yoke-type track rollers 11, 12, 13, 14, 15 have the same diameter,
wherein the pivot points of the yoke-type track rollers 11, 12, 13,
14, 15, in the state depicted, are located on an imagined line such
that all five yoke-type track rollers 11, 12, 13, 14, 15 roller
together with the front deflector roller 10 and the rear deflector
roller 20 along a lower section of the track roller unit 7, which
rests on the ground 5.
[0043] The roller unit body 6 is therefore supported on the lower
section of the track roller unit 7 by the seven rollers 10, 11, 12,
13, 14, 15, 20 in all. It should be noted that the deflector
rollers and the yoke-type track rollers can also have sizes
relative to one another that deviate from the embodiment shown. In
particular, the sizes of the front and the rear deflector rollers
can differ from one another. In addition, the sizes of the
yoke-type track rollers can differ from one another.
[0044] In order to transfer drive power to the track roller unit 4,
the rear deflector roller 20 is expediently driven via a
(non-illustrated) drive train. In order to ensure a belt tension
that is required for reliable operation, a tensioning device is
assigned to the front deflector roller 10. This tensioning device
comprises a cylinder 30, which is acted upon hydraulically by
pressure, is supported at the roller unit body 6 and affects the
position of the front deflector roller via a linkage
(substantially, the arm 16) in order to hold the track belt 7 under
tension by applying a force directed outwardly relative to the
track belt 7 (specifically in this case: toward the front).
[0045] In the case of the tractor 1, all the rollers 10, 11, 12,
13, 14, 15, 20 of the track roller unit 4 are suspended relative to
the roller unit body 6 in order to ensure uniform support along a
majority of the roller unit length also in the event of different
ballasts and tractive forces, in order to reduce the wear on the
track belt during road travel and, in general, to increase driving
comfort. To this end, a particular spring element 31, 32, 33, 34 is
respectively assigned to an individual roller 20 or a group of
rollers 10, 11; 12, 13; 14, 15. These are spring elements that can
be acted upon by fluid, preferably Hydrops with a level control
system, which are supported at one end with respect to the roller
unit body 6 and which, at an opposite end, are each connected to a
linkage to which one or two rollers are coupled. Spring elements
that are acted upon by fluid (such as Hydrops) have the advantage
of compensating in a less abrupt manner and of load adaptability as
compared to steel or rubber springs. In addition, the damper
thereof can vary to a great extent. The front deflector roller 10
is rotatably supported at the elongated arm 16. An upper end of the
arm 16 is connected to the belt tensioning cylinder 30. An opposite
end of the arm 16 is connected to a longitudinal swing arm 17 via a
pivot joint.
[0046] The longitudinal swing arm 17 is rotatably supported, at a
rear end, at the roller unit body 6. A cylinder 31, which is
connected to the longitudinal swing arm 17 in a central section, is
supported at the roller unit body 6 in order to suspend the
longitudinal swing arm 17 with respect to the roller unit body 6. A
yoke-type track roller 11, which is located directly behind the
front deflector roller 10 relative to the vehicle longitudinal axis
3, is rotatably supported at the longitudinal swing arm 17.
Therefore, the front deflector roller 10 and the yoke-type track
roller 11 are jointly suspended with respect to the roller unit
body 6, wherein the suspension takes place, in particular, by a
change in the length (inward deflection) of the cylinder 31. The
cylinder 30, however, is used primarily to maintain a desired belt
tension.
[0047] Another pair of successively arranged yoke-type track
rollers 12, 13 is located behind the yoke-type track roller 11
relative to the vehicle longitudinal axis 3. These are coupled to
the roller unit body 6 via a structure comprising a longitudinal
swing arm 18 and a pendulum arm 27. To this end, the longitudinal
swing arm is rotatably supported, at the upper end thereof, at the
roller unit body 6 and, at an opposite end, accommodates the curved
pendulum arm 27 so as to allow this to pivot about a central
coupling point. A yoke-type track roller 12 and a yoke-type track
roller 13 are rotatably supported at the pendulum arm 27 at either
end of the pendulum arm 27. A cylinder 32 connected to the
longitudinal swing arm 18 is supported at the roller unit body 6 in
order to suspend the longitudinal swing arm 18 and the pendulum arm
27 connected thereto with respect to the roller unit body 6. Due to
the kinematic configuration, the two yoke-type track rollers 12, 13
are jointly suspended with respect to the roller unit body 6,
wherein the suspension takes place by means of a change in the
length (inward deflection) of the cylinder 32.
[0048] In the same manner as described in the preceding paragraph,
the yoke-type track rollers 14, 15 are coupled to the roller unit
body 6 via a structure comprising a longitudinal swing arm 19 and a
pendulum arm 28, wherein the suspension is enabled by a cylinder
33. The mechanical design and the action thereof correspond to that
utilized for the support of the yoke-type track rollers 12, 13, and
so reference is made to those descriptions in order to avoid
repetition.
[0049] The rear deflector roller 20 is supported with respect to
the roller unit body 6 by a longitudinal swing arm 21. A front end,
relative to the vehicle longitudinal axis 3, of the longitudinal
swing arm 21 is rotatably connected to the roller unit body 6. The
rear deflector roller 20 is rotatably supported at an opposite
(rear) end of the longitudinal swing arm 21. A cylinder 34, which
is connected to the longitudinal swing arm 21 in a central section,
is supported relative to the roller unit body 6 in order to suspend
the longitudinal swing arm 21 relative to the roller unit body 6.
The rear deflector roller 20 is therefore suspended relative to the
roller unit body 6, wherein the suspension takes place by a change
in length (inward deflection) of the cylinder 34.
[0050] The kinematic structure of the track roller unit 4 shown in
FIG. 1, in particular the coupling of individual rollers to the
roller unit body 6, the assignment of rollers to spring elements,
the number of rollers, etc., can be configured in a manner that
deviates from the embodiment in diverse manners. FIGS. 1a and 1b
each show, as examples, an altered coupling option for the front
rollers 10, 11.
[0051] According to FIG. 1a, instead of the longitudinal swing arm
17 (FIG. 1), an arrangement is used which comprises a longitudinal
swing arm 24 and a T-shaped component, which is connected thereto
in an articulated manner and comprises a longitudinal beam 23 and a
vertical support 22 rigidly connected thereto. In contrast to the
arrangement according to FIG. 1, the cylinder 31 acts at a
connection point between the longitudinal swing arm 24 and the
longitudinal beam 23.
[0052] According to FIG. 1b, the front deflector roller 10 and the
trailing support wheel 11 are supported separately with respect to
the roller unit body 6. The arm 16, on which the front deflector
roller 10 is supported, is now connected to an angled spring swing
arm 25, which is supported in a central region so as to be
rotatable with respect to the roller unit body 6. A cylinder 31 is
used again in order to suspend the front deflector roller 10, the
cylinder now acting at an upper end of the spring swing arm 25,
however. The yoke-type track roller 11 is supported with respect to
the roller unit body 6 by a separate longitudinal swing arm 26 and
a separate (additional) cylinder 35 is used for the suspension of
the yoke-type track roller 11.
[0053] The mode of operation of the tractor 1, the mechanical
structure of which was described with reference to FIG. 1, is
explained in greater detail in the following with reference to FIG.
2a, 2b, 2c, each of which shows only one track roller unit 4, for
clarity, in various situations of use. The hydraulic connection and
the load distribution underneath the track roller unit are
schematically depicted.
[0054] FIG. 2a shows the track roller unit 4 of the tractor 1 shown
in FIG. 1, including an inner allocation of the roller unit. It is
initially evident that assigned to each of the rollers 20 and the
pairs of rollers 10, 11; 12, 13; 14, 15 is a spring element, which
is acted upon by fluid, in the form of a cylinder 31, 32, 33, 34
("Hydrop"). In particular, the spring element 34 is assigned to the
roller 20, the spring element 31 is assigned to the roller pair 10,
11, the spring element 32 is assigned to the roller pair 12, 13,
and the spring element 33 is assigned to the roller pair 14,
15.
[0055] As depicted in FIG. 2a, the spring element 31 is assigned to
a front suspension unit 40, which forms a virtual front axle 40 of
the tractor 1 (which is not shown in entirety here). By contrast,
the spring elements 32, 33, 34 are assigned to a rear suspension
unit 50, which forms a virtual rear axle 50 of the tractor 1. The
track roller unit 4 is therefore subdivided, in the interior
thereof, into two suspension units, which function as the virtual
front axle 40 and the virtual rear axle 50. In the case shown; the
designation "front wheel" (=front axle 40) and "rear track" (=rear
axle 50) is obvious due to the different effective lengths of the
virtual axles (relative to the respective contact area).
[0056] The cylinder 31 of the virtual front axle 40 comprises a
separate hydraulic supply (which is not depicted in greater
detail), thereby enabling the ground pressure thereof to be set
separately. The cylinders 32, 33 and 34, however, are connected to
a common hydraulic circuit 8. A shut-off valve 38 is arranged at a
connecting tube between the cylinder 32 and the cylinder 33, and a
shut-off valve 38 is arranged at a connecting tube between the
cylinder 33 and the cylinder 34. In the state shown in FIG. 2a,
both shut-off valves 38 are open, and therefore hydraulic fluid
located in the hydraulic circuit 8 can be distributed freely and
with equal pressure onto the cylinders 32, 33, 34. A ground
pressure applied by the center of gravity 9 of the tractor 1 (which
is not depicted in entirety here) onto the roller unit 4 is
accommodated partially by the virtual front axle 40 and partially
by the virtual rear axle 50. The engagement of the cylinders 32,
33, 34 thereby advantageously ensures a uniform distribution of
force underneath the region of the virtual rear axle 50 itself when
there are fluctuating external effects of force, as indicated by
the equal-length bars underneath the rollers 12, 13, 14, 15,
20.
[0057] As shown, there is an unequal distribution of force between
the rollers 10 and 11, which are assigned to the cylinder 31. The
unequal distribution of force is caused by the kinematic
configuration, in particular the mechanical advantages of the
holding structure.
[0058] FIG. 2b shows the state in which the track roller unit 4 is
acted upon by a pulling force, e.g., when a tractor 1 equipped with
the track roller unit 4 performs pulling work, i.e., pulls a plow.
Advantageously, it is now possible (despite the effect of the
tractive force F.sub.Zug) to relieve pressure from the front axle
40 to the extent that the sum of the moments acting on the track
roller unit 4 becomes zero (or nearly zero). This is possible due
to the separate hydraulic supply of the virtual front axle 40 as
compared to the virtual rear axle 50. The distribution of force
underneath the region of the rear axle 50 remains constant due to
the interconnection of the cylinders 32, 33, 34, even when the
tractive force F.sub.Zug changes (again: equal-length bars
underneath the rollers 12, 13, 14, 15, 20), and increases only in
sum (due to the reduced load on the virtual front axle 40).
[0059] If the tractor is operated using a particularly high
tractive force F.sub.Zug, the track roller unit 4 is prevented from
lifting up by a particular overload mode. Reference is made to FIG.
2c in this context. In contrast to the states according to FIGS. 2a
and 2b, a shut-off valve 38 arranged between the cylinders 33 and
34 is closed (indicated by: "0") in the overload mode (FIG. 2c).
The cylinder 34 is therefore acted upon by an increased hydraulic
pressure individually, i.e., hydraulically decoupled from the
cylinders 32, 33. By individual control, the cylinder 34 (even if
the entire tractor 1 is compressed) can apply a greater force, as
indicated in FIG. 2c by the longer bar underneath the roller 20 as
compared to the equally-long bars underneath the rollers 12, 13,
14, 15. Due to the increased cylinder force 34, the pendulum point
of the track roller unit 4 is displaced toward the rear, whereby a
lifting-up of the track roller unit 4 is prevented or is at least
made very difficult.
[0060] In the tractor 1 shown in FIGS. 1 to 2c, the assignment of
the rollers to the virtual front and rear axles 40 and 50,
respectively, is structurally predetermined and, therefore, is
permanent. As an alternative, a changeable assignment of rollers to
basically any number of virtual axles also is conceivable.
[0061] FIGS. 3a and 3b show a track roller unit 4 of a tractor
having a changeable assignment between a central yoke-type track
roller 13 in various operating states (road and field travel). The
track roller unit 4 according to FIGS. 3a and 3b has a structure
explained in the following.
[0062] The front deflector roller 10 is suspended via a separate
cylinder 31, and the rear deflector roller 20 is suspended via a
separate cylinder 34. A front pair of yoke-type track rollers 11,
12 is suspended jointly via a cylinder 36, and a rear pair of
yoke-type track rollers 14, 15 is suspended jointly via a cylinder
33. A support roller 13 arranged between the support roller 12 and
the support roller 14 relative to the vehicle longitudinal axis 3
is suspended via a separate cylinder 37.
[0063] The front cylinders 31, 36 belong to a first hydraulic
circuit 29 and are always acted upon by the same pressure; the rear
cylinders 33, 34 belong to a second hydraulic circuit 8 and are
always acted upon by the same pressure. By shut-off valves 38, the
cylinder 37 can be connected either to the first hydraulic circuit
29, as shown in FIG. 3a, or to the second hydraulic circuit 8, as
shown in FIG. 3b. The track roller unit 4 therefore has a hydraulic
supply, according to which the cylinder 37 is connected either
together with the cylinders 31, 36 to a front suspension unit
(virtual front axle 40) or together with the cylinders 33, 34 to a
rear suspension unit (virtual rear axle 50).
[0064] In this case as well, a uniform distribution of contact
forces is achieved within a suspension unit (virtual front or rear
axle) by the interconnection of associated cylinders, as depicted
by the respective equal-length bars underneath associated
cylinders). Due to the possibility of changing the assignment of
the cylinder 37 to the front or the rear axle, the weight acting on
the track roller unit 4 can be redistributed in order to eliminate
pressure peaks. This can take place depending on the type of load
(with or without tractive force) and/or on the driving state (field
travel, road travel) of the tractor. It is therefore possible to
adjust the pressure distribution underneath the track roller unit 4
independently of the ballast applied to the vehicle overall.
[0065] Given that different hydraulic circuits are generated,
pendulum points P.sub.a, P.sub.b having changeable positions are
generated for each virtual axle 40, 50. In the state according to
FIG. 3a (cylinder 37 assigned to the first hydraulic circuit 29),
the fluid circuit 29 assigned to the front axle 40 has the pendulum
point P.sub.b, while the fluid circuit 8 assigned to the rear axle
50 has the pendulum point P.sub.a.
[0066] In contrast to FIG. 3a, in the state according to FIG. 3b
(the cylinder 37 is assigned to the second hydraulic circuit 8),
the pendulum point P.sub.b of the front axle 40 and the pendulum
point P.sub.a are each displaced substantially toward the
front.
[0067] Basically it is also conceivable that a vehicle operator
manually specifies the assignment of the cylinder 37 to the front
or the rear axle. Preferably, the intended pressure compensation
between the front axle 40 and the rear axle 50 can take place
automatically, in particular depending on operating parameters of
the tractor 1, such as pressure load and/or driving state. To this
end, the cylinders 31, 33, 34, 36, 37 can be assigned sensors for
pressure detection, wherein the assignment of the yoke-type track
roller 13 is carried out depending on the pressure state that is
detected. If a detected pressure difference between the front axle
40 and the rear axle 50 exceeds a predefinable limit, for example,
the cylinder 37 of the central yoke-type track roller 13 is
assigned to the axle at which the excessive hydraulic pressure is
present, in order to reduce the pressure difference between the
axles 40, 50. Advantageously, a hysteresis is provided in a control
of this type, in order to prevent constant switching if the
fluctuations about a limit value are only slight. Further input
variables into such a control could be operating parameters such as
absolute pressure, the forces occurring on yoke-type track rollers
11, 12, 13, 14, 15, the ground speed, or the like.
[0068] The wear on the track roller unit 7 during road travel can
be advantageously reduced by applying a pressure to the cylinder of
the virtual front axle 40 during road travel that is reduced as
compared to a field-travel mode. As an alternative or in addition,
it is possible to lower the force acting on the first roller as
compared to the further rollers of the same axle by the application
of the hydraulics and/or mechanics.
[0069] The tractor described by the invention, including different
variants that were explained, is more compact and maneuverable than
pivot-steered tractors and can therefore also be used on small
fields. The basic design as a two-track tractor makes it possible
to turn about a track or even about the vertical axis of the
vehicle.
[0070] The need to apply ballast precisely is reduced as compared
to conventional two-track tractors. The user merely needs to
roughly apply the ballast to the vehicle by estimating the slip
under the track roller unit, or by a visual assessment. The rear
part of the track roller unit has a homogeneous distribution of
force in the normal operating range. The load on the front part is
small in a design according to FIGS. 2a to 2c, but contributes to
the transfer of tractive force.
[0071] In the case of the concept of "front track-rear track,"
shown in FIGS. 3a and 3b, the distribution of pressure and force is
also homogeneous under the front track rollers. In addition, the
roller unit can automatically compensate for fluctuations in
tractive force (which practically always occur during field work)
up to the underloading or overloading of the vehicle.
[0072] The suspension comfort is substantially increased by the
hydropneumatically suspended track roller unit and, simultaneously,
the tendency of the vehicle to pitch is reduced by the relatively
long length of the track roller unit. As compared to classic
half-track vehicles or vehicles having four mounted tracks, the
vehicle described also can be steered better due to differential
steering. Track bar wear is reduced by the active control of the
front rollers.
[0073] As compared to the half-track design according to WO
2013/113484 A2, the design according to the invention does not
require a front axle. Thus, there also is no need for coordination
with wheels, which may be driven, on the front axle, nor is there a
need for synchronization between differential steering of the rear
axle and steering of the front axle.
[0074] Another advantage of this inventive full track design, and
agricultural vehicle comprising same, results from the large
contact area, which also makes it usable, in principle, for other
agricultural machines, such as, e.g., harvesting machines.
LIST OF REFERENCE NUMBERS
[0075] 1 tractor [0076] 2 vehicle frame [0077] 3 vehicle
longitudinal axis [0078] 4 track roller unit [0079] 5 ground [0080]
6 roller unit body [0081] 7 track belt [0082] 8 hydraulic circuit
[0083] 9 center of gravity [0084] 10 front deflector roll [0085] 11
yoke-type track roller [0086] 12 yoke-type track roller [0087] 13
yoke-type track roller [0088] 14 yoke-type track roller [0089] 15
yoke-type track roller [0090] 16 arm [0091] 17 longitudinal swing
arm [0092] 18 longitudinal swing arm [0093] 19 longitudinal swing
arm [0094] 20 rear deflector roll [0095] 21 longitudinal swing arm
[0096] 22 vertical support [0097] 23 longitudinal support [0098] 24
longitudinal swing arm [0099] 25 spring swing arm [0100] 26
longitudinal swing arm [0101] 27 pendulum arm [0102] 28 pendulum
arm [0103] 29 hydraulic circuit [0104] 30 belt tensioning cylinder
[0105] 31 cylinder [0106] 32 cylinder [0107] 33 cylinder [0108] 34
cylinder [0109] 35 cylinder [0110] 36 cylinder [0111] 37 cylinder
[0112] 38 shutoff valve [0113] 40 (virtual) front axle [0114] 50
(virtual) rear axle [0115] F.sub.Zug tractive force [0116] P.sub.a
rear pendulum point [0117] P.sub.b front pendulum point
[0118] As will be evident to persons skilled in the art, the
foregoing detailed description and figures are presented as
examples of the invention, and that variations are contemplated
that do not depart from the fair scope of the teachings and
descriptions set forth in this disclosure. The foregoing is not
intended to limit what has been invented, except to the extent that
the following claims so limit that.
* * * * *